Britannica Sources used in this answer

How does atomic number determine an element’s position on the periodic table?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Bohr model diagram of a hydrogen atom showing a green nucleus labeled H, a single electron orbit, and text with atomic mass 1.008 and electron configuration 1. — atom The Bohr model describes the structure of atoms, in this case hydrogen.

The atomic number is the fundamental value that determines an element’s specific position on the periodic table. It is defined as the total number of protons found within the nucleus of an atom.123

Elements are arranged on the periodic table in sequential order based on their increasing atomic number. Because the number of protons in the nucleus is unique to each element, this value serves as the primary identifier that distinguishes one chemical element from another. In a neutral atom, the atomic number also corresponds to the number of electrons surrounding the nucleus, which dictates the element's chemical characteristics.143

By organizing elements according to this increasing sequence, the periodic table reveals the "periodic law," a recurring pattern where elements in the same column, or group, exhibit similar chemical properties.4